Physiology of Seed and Fiber Development

The ovules of cotton are composed of the immature seed (embryo and seed coat) and developing fiber. By the coincidence of their proximity, fiber and seed are competing sinks fed through a common funiculus. Partitioning of photosynthate between fiber and seed has been altered by plant breeding. Selection for high yield has increased the thickness of the fiber wall, as indicated by increased micronaire readings (Bridge and Meredith, 1983; Wells and Meredith, 1984). Concomitantly, boll and seed size has decreased (Bridge et al., 1971). These changes are not without an agronomic cost. Small seeds have poorer germination and lower seedling survival. Post-harvest problems are caused by small seed as well: small seed will often pass through the gin with the fiber. The agronomic impact of small seed and the economic impact of fiber make a compelling argument for understanding the physiological relationships between fiber and seed development and the physiology associated with specific events of fiber development.